A U.N. special investigator warns Burundi could slip back into open warfare unless the international community takes urgent preventive action.

Pablo de Greiff, a U.N. special investigator on mass violations, said much has happened since he visited Burundi in December — and none of it good. He said Burundi has turned away from the peaceful path it had followed since the 2000 Arusha agreement that ended the country's civil war.

He said the government of President Pierre Nkurunziza is no longer attempting to build a society based on the rule of law, and that the tradition of impunity from past decades has become further entrenched and is being used as a tool of repression and violence.

De Greiff said he presented his concerns to the U.N. Human Rights Council in hopes member states understand the gravity of the situation unfolding in Burundi, and take measures to head off a disaster.

“Here, I want to be very honest — trying to sound a very urgent, cautionary call to the international community not to wait until we have another tragedy in our hands before we take action,” he said.

About 300,000 people were killed in Burundi during the civil war.

The country was relatively peaceful in recent years until the end of April, when the president announced he would seek a controversial third term. Since then, de Greiff said, there have been more than 100 killings, hundreds of arbitrary arrests, and many cases of torture and ill-treatment.

He said none of these cases is being investigated, except for one that involves a government official.

The president was re-elected in July, but tension remains between his supporters and those who say he violated the two-term limit in the constitution.

The U.N. investigator says the international community and regional governments cannot afford to simply stand by and wait for new mass atrocities to recur in Burundi. He warns this would risk a major conflict in the Great Lakes region, with unpredictable and frightening results.